Known IGCC power generation systems may include a gasification system that is integrated with at least one power producing turbine system. For example, known gasifiers may convert a mixture of fuel, air or oxygen, steam, and other additives into an output of a partially combusted gas, typically referred to as a “syngas”. These hot combustion gases are supplied to the combustor of a gas turbine engine. The gas turbine engine, in turn, powers a generator for the production of electrical power or drive another type of load. Exhaust from the gas turbine engine may be supplied to a heat recovery steam generator (“HRSG”) so as to generate steam for a steam turbine. The power generated by the steam turbine also may drive an electrical generator or another type of load. Similar types of power generation systems may be known.
The gasification process may use a water gas shift reactor. The basic water gas shift reaction is as follows: CO+H2O<->CO2+H2. In order to improve the shift reaction, high pressure steam may be mixed with the raw syngas entering the water gas shift reactor so as to increase the H2O/CO ratio. The source of the steam is generally taken from the bottoming cycle or from cooling the syngas in a high/low temperature gas cooling section. The reaction also is temperature sensitive.
The efficiency of the overall IGCC system with CO2 capture, however, may be reduced given the high pressure steam requirements for the water gas shift reactor. Specifically, the high pressure steam taken for the saturation of the raw syngas involves a performance penalty in that the steam is not available for expansion work in a steam turbine. The diversion therefore may reduce overall system efficiency, net output, and heat rate.
There is therefore a desire therefore for an improved integrated gas combined cycle power generation system with CO2 capture. Such a system preferably may maintain adequate CO2 capture while increasing overall system efficiency and performance.